- Chronic use of therapies that may modify immune response, such as IV immuneglobulin and systemic corticosteroids (in doses of > 20 mg/day prednisone equivalent for periods exceeding 10 days). The following exceptions are permitted and will not exclude study participation: use of corticosteroid nasal spray for rhinitis, topical corticosteroids for an acute uncomplicated dermatitis; or a short course (duration of 10 days or less, or a single injection) of corticosteroid for a non-chronic condition (based on investigator clinical judgment) at least 2 weeks prior to enrollment in this study.